The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
An internal combustion engine (ICE) combusts an air/fuel mixture within cylinders to drive pistons, which produces drive torque. Operation of the ICE, such as spark timing, air intake flow rates, and fuel injection amounts and timing, are controlled based on various monitored parameters. The parameters may include, engine speed, engine temperature, mass air flow, manifold absolute pressure, amounts of NOx out of an engine, etc. Sensors are often used to measure the parameters.
Operation of an ICE may be controlled based on a determination of an amount of NOx output from the ICE. The amount of NOx output may be measured via a NOx sensor. As an alternative, the amount of NOx output may be estimated based on measured pressures within one or more cylinders of the ICE. This however requires one or more pressure sensors in one or more cylinders of the ICE. Although both of these techniques provide fast and accurate estimations of NOx output, both of these techniques require at least one sensor (a NOx sensor or one or more pressure sensors) for the measurement of NOx and/or in-cylinder pressures of the ICE.